1. Industrial Field of the Invention
The present invention relates to a flat motor and an exposure device, and more particularly, to a flat motor for driving a moving element (slider) two-dimensionally by electromagnetic force and to an exposure device using the flat motor for a substrate stage unit.
2. Description of the Related Art
Conventionally, exposure devices are used in a lithography process for manufacturing semiconductor devices, liquid crystal devices and the like to transfer a pattern formed on a mask or a reticle (hereinafter, generically called xe2x80x9creticlexe2x80x9d) onto a substrate such as a wafer, a glass plate or the like, on which a resist of the like is coated, through a projecting optical system.
In the exposure device, a wafer is held on a wafer holder by vacuum adsorption or the like because it must be positioned at an exposing position with pinpoint accuracy, and the wafer holder is secured on a wafer table.
Conventionally, a drive unit composed of a rotating type motor and a conversion mechanism for converting a rotating motion to a linear motion is often used as a drive unit for moving an object to be controlled such as the wafer table and the like on a straight line or a plane or positioning the object at a target position. Recently, however, a stage unit has been developed for positioning an object to be controlled by driving it two-dimensionally in a contact-free fashion so that the object to be controlled can be positioned at a higher speed with pinpoint accuracy without being affected by the accuracy of a mechanical guide surface and the like and that the life of the stage unit can be increased by the avoidance of mechanical friction. A variable-magnetic-resistance drive type flat motor is known as the drive source of the non-contact drive type stage unit.
At present, the variable-magnetic-resistance drive type flat motor is mainly arranged by coupling the two axes of variable-magnetic-resistance drive type linear pulse motors as in a Sawyer motor. The variable-magnetic-resistance drive type linear pulse motor includes a stator, which is composed of a sheet-shaped magnetic body having, for example, uneven tooth portions formed thereon along a lengthwise direction at equal intervals and a slider, which is composed of a plurality of armature coils confronting the uneven tooth portions of the stator, having uneven portions whose phase is different from that of the above uneven tooth portions and coupled through permanent magnets. Then, the slider is driven making use of force generated so as to minimize a magnetic resistance between the stator and the slider at each timing. That is, the slider is advanced stepwise by regulating and controlling the current values and the phases of pulse currents supplied to the respective armature coils.
In the variable-magnetic-resistance drive type flat motor, it is necessary to obtain large drive force to realize positioning at a high speed by using it in a precise positioning unit. For this purpose, a large current must be necessarily flown to armature coils. As a result, a large problem is arisen in the heat generated from the armature coils.
However, since the armature coils are not cooled in the variable-magnetic-resistance drive type flat motor at present, it is difficult to apply the flat motor to the precise positioning unit.
Further, there has been also developed a flat motor which is obtained by two-dimensionally developing a linear motor and driven by Lorentz electromagnetic force (for example, U.S. Pat. No. 5,196,745). It is said that the Lorentz electromagnetic-force type flat motor is promising as a stage drive source in future because it is excellent in controllability, thrust force linearity and positioning characteristic.
However, a large current must be flown to armature coils also in the Lorentz electromagnetic-force flat motor to obtain a large amount of thrust force and thus the armature coils act as a heat generating source. Therefore, the environment of a precise positioning device is taken into consideration, it is indispensable to design a cooling system to realize a flat motor in which a thermal effect is lowered.
Further, in the Lorentz electromagnetic-force-drive flat motor and the like, an armature unit including armature coils is usually arranged as a stator for the convenience of supplying a current to the armature coils. However, when the flat motor arranged as described above is employed as the drive source of the substrate stage of a projecting/exposing device including a projecting optical system, the stator is often physically secured to a main body column by which the projecting optical system is held. In this case, the projecting optical system is oscillated by the reaction force acting on the stator when a slider is driven, which results in the dislocation of a position to which a pattern is transferred and the deterioration of uniformity of a line width. However, since the exposure device using the flat motor is now at the start of its development, a mechanism for not transmitting the reaction force acting on the stator such as the armature unit and the like to a structural member for supporting it is not yet known.
A first object of the present invention, which was made in the above circumstances, is to provide a flat motor cable of suppressing a thermal effect on a peripheral environment.
A second object of the present invention is to provide an exposure device capable of carrying out exposure with pinpoint accuracy while maintaining a high throughput.
A flat motor device according to the invention described in claim 1 is characterized by comprising a moving unit (40, 42) moving along a predetermined moving surface; and a fixed unit (32) having the moving surface formed on the side thereof confronting the moving unit, wherein one of the moving unit and the fixed unit includes a pole unit (40); and the other of the moving unit and the fixed unit includes armature coils (32), a heat insulating chamber (62) disposed to the armature coils on the moving surface side thereof and a cooling chamber (64) disposed to the armature coils on the side thereof opposite to the moving surface.
According to the flat motor device, when currents are supplied to the armature coils constituting the moving unit or the fixed unit, the moving unit is moved along the moving surface by the electromagnetic force generated by electromagnetic interaction between the armature coils and (the magnets constituting) the pole unit. When the moving unit is to be continuously moved in a certain direction, currents are supplied to the armature coils which confront the pole unit (magnets) (in the case of a moving magnet type) or to all the armature coils (in the case of a moving coil type) in accordance with the moving position of the moving unit. With this operation, the armature coils to which the respective currents are supplied generate heat. In this case, the heat insulating chamber is disposed to the armature coils on the moving surface side thereof and the cooling chamber is disposed thereto on the side thereof opposite to the moving surface, respectively. As a result, the transmission of the heat generated by the armature coils to the moving surface side is suppressed or prevented by the heat insulating action of the heat insulating chamber, and the armature coils are cooled by the cooling chamber. Therefore, the armature coils can be cooled as well as the effect of the heat generated by the armature coils on a peripheral environment can be suppressed.
In this case, various types of heat insulating and cooling methods can be contemplated and various arrangements of the heat insulating chamber and the cooling chamber can be contemplated accordingly. For example, as shown in the invention described in claim 2, the interiors of the heat insulating chamber (62) and the cooling chamber (64) may be arranged as flow passages in which fluids having different flow conditions flow. In this case, the armature coils can be cooled from the side opposite to the moving surface by the heat exchange with the fluid in the cooling chamber as well as the transmission of the heat generated by the armature coils to the moving surface side can be suppressed or prevented by the heat insulating action of the of the fluid in the heat insulating chamber similarly to the invention described in claim 1 so as to suppress a thermal effect on the peripheral environment by flowing the same or different fluids having different flow conditions in the flow passages of the heat insulating chamber and the cooling chamber.
In this case, as shown in the invention described in claim 3, the flat motor device may include a fluid supply device (102) for supplying first and second fluids into the first and second fluid passages by regulating flow states so that the flow of the fluid in the interior of the heat insulating chamber is made to a laminar flow and the flow in the interior of the fluid in the cooling chamber is made to an approximate transition flow. In this case, the transmission of heat to the moving surface side can be effectively prevented by the formation of a temperature boundary layer in the flow of the first fluid in the heat insulating chamber as well as heat can be effectively removed from the armature coils by the second fluid because the heat transfer coefficient between the second fluid in the cooling chamber and the wall on the armature coils side is increased.
In this case, as shown in the invention described in claim 4, it is preferable that the fluid supply device (102) supplied the fluids into the respective flow passages so that the flowing direction of the fluid flowing in the heat insulating chamber (62) and the flowing direction of the fluid flowing in the cooling chamber (64) are made to the same direction or an opposite direction. When the flowing direction of the fluid flowing in the heat insulating chamber is the same as the flowing direction of the fluid flowing in the cooling chamber, one of the moving unit and the fixed unit which includes the armature coils can be approximately uniformly cooled. Further, when the flowing direction of the fluid flowing in the heat insulating chamber is opposite to the flowing direction of the fluid flowing in the cooling chamber, the temperature of the one of the units can be lowered as a whole.
In the respective inventions described in claims 2-4, the fixed unit may include a first wall (57) having the moving surface formed on one side thereof and a deformation preventing member (56a, 68) for supporting the first wall from the other side thereof as shown in the invention described in claim 5. In the case of an air floating type flat motor device, a moving surface on a fixed unit side ordinarily also act as an air guide. In this case, since a first wall on which a moving surface is disposed is supported by a deformation preventing member, the moving surface is arranged as a rigid structure capable of resisting against an air pressure, whereby a moving unit can be supported with highly rigidity.
In this case, as shown in the invention described in claim 6, when the fixed unit (32) includes, in the interior thereof, the armature coils (34) disposed along the moving surface (32a), the heat insulating chamber (62) disposed to the armature coils on the moving surface side thereof and the cooling chamber (64) disposed to the armature coils on the side thereof opposite to the moving surface side, it is preferable that the cross-sectional shape of the deformation preventing member (56a, 68) is formed to a wing shape in the flow passage portion thereof in the heat insulating chamber (62). This is because that while the flows of the first and second fluids may be disturbed by the deformation preventing member which is located in the flows of the first and second fluids in the heat insulating chamber and the cooling chamber, it can be suppressed that the fluid in the fluid passage in the heat insulating chamber is made to a transition flow state or to a turbulent flow state in such a case.
In this case, a plate-shaped partition member (60) may be disposed to the armature coils (34) on the moving surface (32a) side thereof, and the flow passage (62) in the heat insulating chamber may be formed between the first wall (57) having the moving surface formed on the one side thereof and the partition member as shown in the invention described in claim 7.
In the respective inventions described in claims 2-7, a temperature controller (106, 108) may be provided to precontrol the temperatures of the respective fluids to temperatures lower than the atmospheric temperature of the base (32) as shown in the invention described in claim 8. In this case, heat can be more effectively removed from the armature coils.
In the respective inventions described in claims 1-8, the flat motor device may further include a holding member (56B, 72) isolated from the first member (56A) having the moving surface (32a) formed thereon with respect to oscillation for holding the armature coils or the pole unit constituting the fixed unit (32) as shown in the invention described in claim 9. In this case, when the moving unit is moved, the reaction force thereof acts on the armature coils or the pole unit constituting the fixed device. However, since the armature coils or the pole unit is held by the holding member which is isolated from the first member with reference to oscillation, the reaction force is not transmitted to the first member through the armature coils or the pole unit. Therefore, the oscillation of the first member (moving surface) caused by the drive of the moving unit can be prevented.
In the invention described in claim 10, a flat motor device provided with a moving element (40, 42), which is moved along a predetermined surface (32a) by electromagnetic force, and a base (32), which includes a first member (56A) having the moving surface formed on the side thereof confronting the moving element and a stator (34, 58) disposed in the interior thereof along moving surface, is characterized in that one of the moving element and the stator includes a pole unit and the other of the moving element and the stator includes armature coils, and the flat motor device includes a holding member (56B, 72) isolated from the first member with respect to oscillation for holding the stator.
According to the flat motor device, when the moving element is moved along the moving surface by the electromagnetic force, the stator in the base receives the reaction force thereof. However, since the stator is held by the holding member which is isolated from the first member, on which the moving surface is formed, with respect to oscillation, the reaction force is only transmitted to the ground (floor surface) through the stator and the holding member and is not transmitted to the first member. Therefore, the oscillation of the first member (moving surface) caused by the drive of the moving element can be prevented.
The invention described in claim 11 is an exposure device for transferring a predetermined pattern onto a substrate which is characterized in that the exposure device uses the flat motor device according to any one of claims 1-10 for a substrate stage unit for driving the substrate.
According to the exposure device, since the flat motor device according to any one of claims 1-10 is used for the substrate stage unit, the substrate can be driven in a contact-free fashion by electromagnetic force and further a thermal effect resulting from the heat generated by the armature coils can be effectively reduced. The fluctuations in air of the beams of an interferometer for measuring the position of a wafer, and the like can be suppressing thereby. Accordingly, the position of a substrate can be precisely controlled at a high speed, and, as a result, exposure can be carried out with high exposing accuracy while enhancing a throughput. In particular, in a projecting exposure device including a projecting optical system, it is preferable to use the flat motor device according to claim 9 or 10 to a substrate stage unit. In this case, even if a first member on which a moving surface is disposed is secured to a main body column for holding the projecting optical system, the first member and the main body column and further the projecting optical system held by the main body column are not oscillated by the reaction force acting on a fixed unit (stator) when a substrate stage including a moving unit (moving element) is moved. As a result, the dislocation of a pattern transferred position, the deterioration of the uniformity of a line width, and the like are not caused, whereby exposing accuracy can be more enhanced.